Take it mercedes and see if they can help. Especially with the Tranny - its a stock 722.6 box in several of their cars and the issues would be well known as well as the fixes. I guarantee they would see half a dozen of these trannys for service a month.
To be safe though - I would know as much about the problem as possible so you can talk turkey with the techs. Many reports of them ...change this....change that...of course they are not paying. They might do a little more research and thinking if they had to pay for "change this" 's that didnt work. But that aint the way it is.
A bit like your doctor....."hmmm...lets see now".
As for fluid/parts, every town has one - an indie Mercedes mechanic - they worked for meceredes for 10 years and then went out on their own and do mainly mercedes.
I always
1) use my indie mercedes specialist and then
2) often double check what he has told me against either this forum or the benzworld slk forum. There's also slkworld. Just in case he's too entrenched in his own world - they can be a little like that (well mine can) since they arent in the MB training/education loop so much and old school, independent and not so open to open to new ideas - particularly ones that may challenge their own view.
look here,
http://www.benzworld.org/forums/r170...ion-flush.html
there is a tranny oil change procedure. Its a 1hr procedure for the "basically compentent" and apart from ATFluid, will set you back about $20 for gasket and filter kit....oh and $1.70 for 3 foot of that stretchy curtain wire*. I'm hoping it may fix some of my issues. MB spec ATF will be about $100 - dont use anything else. Tranny's are all about friction, slip and viscoisty and hence the properties of a particular ATF are paramount. I'll see if I can get a PN code - chasing the issue myself.
*SImply run the flexy curtain wire down the dipstick tube until you are sure it hits the bottom of the tranny sump and oila! Careful - it may catch halfway down - give it a jiggle. Dont worry so much about the locking tab - the cap will stay on the O-ring regardless of the locking tab (for years reportedly).